not all albums are shown - album art in confusion, multiple values as a reason?

[simoncn]

The Casals, Schulhoff album and the Tsutsumi, Turini album are both tagged "Album: Cellosonate Nr. 3, op. 69, Artist: Beethoven". Because the Album and Artist tags match and the albums have multiple discs, these albums are being merged and this is causing the problems you are seeing.

The best way to fix this is to change the Artist tag values to something based on the performing artists rather than the composer name.